Syrian opposition representatives have taken the country's seat for the first time at an Arab League summit, a significant diplomatic boost for the forces fighting president Bashar Assad.

In a ceremonious entrance accompanied by applause, a delegation led by Mouaz al-Khatib, the former president of the main opposition alliance - the Western-backed Syrian National Coalition - took the seats assigned for Syria at the invitation of Qatar's emir, Sheik Hamad bin Khalifa Al Thani.

The decision for the opposition to take Syria's seat was made at the recommendation of Arab foreign ministers earlier this week in the Qatari capital, Doha. The Arab League in 2011 suspended the Syrian government's membership in the organisation in punishment for the regime's crackdown on opponents.

The Qatari ruler, who chairs the summit, said the Syrian opposition deserves "this representation because of the popular legitimacy they have won at home and the broad support they won abroad and the historic role they have assumed in leading the revolution and preparing for building the new Syria."

The diplomatic triumph and Qatar's praise, however, could not conceal the disarray within the top ranks of the Syrian opposition.

Besides Mr al-Khatib, the Syrian delegation included Ghassan Hitto, recently elected prime minister of a planned interim government to administer rebel-held areas in Syria, and two prominent opposition figures, George Sabra and Suheir Atassi.

Addressing the gathering, Mr al-Khatib thanked the Arab League for granting the seat to the opposition. "It is part of the restoration of legitimacy that the people of Syria have long been robbed of," he said.

He lamented the inaction of several foreign governments, which he did not name, toward the Syrian crisis and spoke emotionally of the suffering of the civilians in his country.

He also defended the presence in Syria of foreign jihadis, saying the militants were there to help defend a people under attack but added that those more needed by their families in their own countries should leave.

Even as rebel fighters gain more territory on the ground in their fight against Assad's troops, their mostly exile political leadership has been thrown into disarray. Mr al-Khatib announced his resignation on Sunday because of what he described as restrictions on his work and frustration with the level of international aid for the opposition.